Re: gum/dichromate ratios

From: Dave Rose ^lt;>
Date: 11/10/05-07:40:40 PM Z
Message-id: <003901c5e660$ec1a90a0$11ac9045@dave6m4323wvj7>

Rather than mix chunks of gum with water, why not use a gum arabic solution?
It's readily available from any well stocked dealer that carries printing
supplies. A one gallon jug will last for many years of gum printing.

Dave in Wyoming

> I have to agree with Chris here - the amm.di.needs to be at about 15% for
> digital negs. I found this out by a lot of experimentation......
> I also mix my gum "as needed" rather than keeping a bottle full, that way
> I can't get back to printing for a while, I'm not throwing old gum out, or
> using toxic preservatives. I'm very aware that I'm exposing myself to
> chemistry all the time, even with the precautions I take. You might say
> paranoid about it :)
> Kate
> -----Original Message-----
> From: Christina Z. Anderson []
> Sent: Friday, 11 November 2005 3:19 a.m.
> To:
> Subject: Re: gum/dichromate ratios
> I use I part gum powder to either 1 or 2 parts water, weight to volume,
> then use my gum/pigmnet to dichromate as 1:1, but the dichromate part of
> equation is either 1/2 water 1/2 saturated dichromate or 3/4 water 1/4
> saturated dichromate. In other words, I only use a 15% or 7.5% dichromate
> solution in my mix.
> Lately i switched to the 15% as I'm testing my new curves and colorized
> and such, just because the layer is very stable and if I want to let it
> automatically develop (e.g. sit face down in water) the color falls off
> fine, or if I want to spray develop it holds up to spray perfectly. But I
> don't use saturated dichromate 1:1 any more since switching to
> diginegs.
> Chris
> >I use 1 part of saturated dichromate to 2 or 3 parts of gum/pigment
> >mixture. My gum is commercial 14 baume. Less toxic and expensive
> >(ammonium dichromate) the better. As you can see the ratios are flexible
> >and you will do best finding your own workflow.
> > Marek M
> > Houston
Received on Thu Nov 10 19:38:02 2005

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